Field of the Invention
The present invention relates to a projection-type display apparatus using a reflective light valve, especially, a DMD in which micromirrors are arranged to perform modulation by deflection of light by the micromirrors.
Description of the Related Art
In recent years, a market of projectors greatly expanded as personal computers became widely used. As light valves (image display devices) used in these projectors, transmissive or reflective liquid crystal display devices, a DMD (Digital Micromirror Device) device, in which micromirrors are regularly arranged, and the like are known. Especially, the DMD device using micromirrors is appropriate to reduce the size of a projector, because the DMD device has a high response speed, and the projector is structurable in such a manner that illumination light of each of RGB is sequentially output to a single-panel light valve by time division.
In projectors, basically three types of optical system using a DMD device, as a light valve, are known. The first type separates rays of illumination light and rays of projection light from each other by using a total reflection prism. However, since the total reflection prism is used, there is a problem that the size of the apparatus becomes large, and the cost increases. In the second type, an entrance pupil is positioned toward the reduction side in a projection lens, and rays of illumination light and rays of projection light are separated from each other by greatly shifting the projection lens with respect to a light valve. However, since separation of rays of illumination light and rays of projection light is imperfect, illumination becomes uneven. Further, there is a problem that a pupil toward the magnification side is not positioned symmetrically with respect to the center of a projection image.
Therefore, when the size of a projector is tried to be reduced, the third type is desirable. In the third type, illumination light and projection light are separated from each other by arranging a field lens in the vicinity of a light valve. As projection-type display apparatuses configured in this manner, apparatuses disclosed in Specification of Japanese Patent No. 4159840 (Patent Document 1), Specification of Japanese Patent No. 4599391 (Patent Document 2) and Specification of U.S. Pat. No. 7,204,613 (Patent Document 3) are known.